Systems using a computer are known to monitor the state of a battery supplying power to an electrical system, such as described in U.S. Pat. No. 4,937,528, Method For Monitoring Aircraft Battery Status" and U.S. Pat. No. 5,281,919, "Automotive Battery Status Monitor", which are owned by the assignee of the subject application. In those patents, the battery being monitored supplies power to the electrical system of various types of vehicles, as well as to the computer that performs the monitoring. The computer receives input data such as the battery voltage and current being drawn by the electrical system and monitors, analyzes and computes battery status factors, such as battery internal resistance, polarization resistance, state of charge and remaining capacity.
It is sometimes desired to prevent excessive power drain of the battery. One way to accomplish this would be to power on the computer only periodically to perform its necessary computations and analysis. At other times, the computer would be deactivated and not supplied with electrical power.